Sycamore mine?

Sycamore mine?

Observation - Sycamore mine? - UK and Ireland. Description: Sycamore leaf with brown circular patches from a young tree in a patch of broadleaved woodland. I have not got very far in trying to identify these. I have looked at the leaf miner sites but cannot find a match - Heterarthrus cuneifrons is a candidate

Sycamore leaf with brown circular patches from a young tree in a patch of broadleaved woodland. I have not got very far in trying to identify these.

I have looked at the leaf miner sites but cannot find a match - Heterarthrus cuneifrons is a candidate in the shape but these "mines" other than being round do not look like the examples shown.

As a long shot I tried the AIDGAP guide for galls, to no avail.

The dark areas within the patches may be frass, so they may be mines, but I am sure there may be other causes.

Any suggestions?